1. Field of the Invention
The present invention relates generally to an improved anti-siphon valve and, more particularly, to a small and inexpensive valve with a positive valve action initiated by a pressure drop in a water supply line, the valving action occurring independently of the physical location or orientation of the valve.
2. Description of the Prior Art
Anti-siphon valves are inserted into a water supply line between a water source and the end of the water supply line to prevent the backflow of possibly contaminated water from the end of the supply line into the supply line on the source side of the anti-siphon valve. The problem arises when a drop in pressure in the line on the supply side of the anti-siphon valve creates a partial vacuum in the supply line tending to draw water backwards into the supply line. In many municipalities such anti-siphon valves are required by local codes.
A closely related valve is the vacuum breaker, which also prevents an undesired reverse flow of water into the outlet end of the supply line. The difference between anti-siphon valves and vacuum breakers is that anti-siphon valves typically include an air vent to allow the anti-siphon valve to close whenever pressure in the supply line drops below ambient air pressure. Vacuum breakers, on the other hand, are generally operated by fluid flow backwards through the valve, the backwards flow path tending to force a valve element against a valve seat to block such reverse fluid flow.
Anti-siphon and vacuum breaker valves typically use one of three valving mechanisms to block reverse fluid flow through the valve. These three mechanisms are a cylindrical valve element, a flap-type valve element, and a spherical valve element. Examples of such devices and the drawbacks of each such device are illustrated below.
The spherical type valve element is illustrated in U.S. Pat. No. 4,064,896, to Trenary, in which a vacuum breaker with a ball-shaped valve element operated solely by fluid flow through the valve as illustrated. The Trenary device includes a plurality of air vents in the valve housing, together with a floating flat annular washer to close the air vents when the valve element, a floating ball, is open. The structure and operation of the Trenary vacuum breaker are substantially different from those of the present invention.
The second type of valve is the flap type, which is illustrated in U.S. Pat. No. 3,470,898, to Langdon, and by U.S. Pat. No. 2,594,999, to Robinson. Both of these patents have a relatively flat, circular valve element which moves forward and backward relative to a valve seat depending on fluid flow through the valve. The Langdon device requires a great deal of precision in the manufacture of the valve to assure a complete seal against reverse flow through the valve. It may be immediately appreciated that such high degree of precision makes the Langdon device relatively costly to manufacture, which disadvantage is not aided by the fact that the Langdon device includes a relatively high number of parts having numerous machined surfaces. In addition, the Langdon device is not easily adaptable to being manufactured in a relatively small package due to the machined surfaces and the high degree of precision in manufacturing the device.
The Robinson device also has a relatively large number of parts and numerous machined surfaces, which make the device relatively complex and expensive to manufacture. In addition, while the Robinson device does have an air vent, it must be utilized in a normalized position to allow the flap valve mechanism to function normally. Failure to properly orient the device will allow completely unrestricted reverse flow through the device, thus restricting the usefulness of the Robinson device to an application in which the relatively large valve may be installed in a proper orientation.
The third type of anti-siphon valve utilizing a piston valve mechanism is illustrated by U.S. Pat. No. 2,627,278, to Somers. Like the previous devices, the Somers valve requires a number of machined surfaces, and contains not less than six parts. In addition, the Somers device must also be properly oriented to insure operation of the device to prevent reverse fluid flow through the valve. While the Somers device is capable of being manufactured in a moderately small package, the complexity of the device precludes a very small package.
It may therefore be appreciated that there exists a substantial need for an anti-siphon valve of a simple design enabling the inexpensive manufacture of the valve. The valve must be very small, long lasting and corrosion resistant, and must work regardless of what position the valve is oriented in due to different installation requirements. The valve must close whenever a pressure drop occurs in the supply line, not just when reverse fluid flow occurs.
In addition, it is desirable that the valve be adaptable to include a nozzle element for use in combination with a toilet seat as a jet for a bidet device. It may be appreciated that since the valve will be installed on the toilet seat, it must therefore be fairly small. Finally, it is desirable that the valve include an air vent and that the design of the valve insure consistent operation to eliminate the possibility of reverse fluid flow through the valve.